Kel'Thuzad

By the period shortly before the Second War on Azeroth, Kel'Thuzad was a member of the Council of Six, the high council of the Kirin Tor - the masters of Dalaran.
Of the Kirin Tor's leaders, Kel'Thuzad was the most eager to gain access to the Guardian's Library - the depository of knowledge hoarded by Medivh in his tower of Karazhan - and thus was most upset when the library was lost.
After Medivh's death, Kel'Thuzad and the other senior members of the Kirin Tor questioned Medivh's apprentice, Khadgar, about what happened; Kel'Thuzad seemed particularly interested in discovering more about the mysterious Order of Tirisfal, which - as he pointed out to Antonidas, the leader of the Kirin Tor - was relevant when discussing Medivh.
Some time after,a handful of powerful individuals, scattered across the world, heard the Lich King's mental summons from Northrend.
Most notable of them was the Archmage Kel'Thuzad from the magical nation of Dalaran.

Kel'Thuzad was one of the senior members of the Kirin Tor - Dalaran's ruling council - and had been considered a maverick for years due to his insistence on studying the forbidden arts of necromancy.
Driven to learn all he could of the magical world and its shadowy wonders, he was frustrated by what he saw as his peers' outmoded and unimaginative precepts.
Upon hearing the powerful summons from Northrend, the archmage bent all of his considerable will to communing with the mysterious voice.
Convinced that the Kirin Tor was too squeamish to seize the power and knowledge inherent in the dark arts, he vowed to learn what he could from the immensely powerful being named the Lich King.
Forsaking his fortune and prestigious political standing, Kel'Thuzad abandoned the ways of the Kirin Tor and left Dalaran forever.
Prodded by the Lich King's persistent voice in his mind, he sold his vast holdings and stored away his fortunes.
Travelling alone over many leagues of both land and sea, he finally reached the frozen shores of Northrend.
Intent on reaching Icecrown and offering his services to the Lich King, the archmage passed through the ravaged, war-torn ruins of Azjol-Nerub.
Kel'Thuzad saw firsthand the scope and ferocity of Ner'zhul's power. He began to believe that allying himself with the mysterious Lich King would not only be wise, but potentially fruitful.

After long months of trekking through the harsh Arctic wastelands, Kel'Thuzad finally reached the dark glacier of Icecrown.
He boldly approached Ner'zhul's dark citadel and was shocked when the silent undead guardsmen let him pass as though he was expected.
Kel'Thuzad descended deep into the cold earth and found his way down to the bottom of the glacier.

Within the endless cavern of ice and shadows, he prostrated himself before the Frozen Throne and offered his soul to the dark lord of the dead.
(The full version of his flight from Dalaran and encounter in Icecrown, where he meets Anub'arak and realizes, too late, the full plans of the Lich King, is told in the short story, The Road to Damnation).
The Lich King was pleased with his latest conscript.
He promised Kel'Thuzad immortality and great power in exchange for his loyalty and obedience.
Kel'Thuzad, eager for dark knowledge and power, accepted his first great mission: to go into the world of men and found a new religion that would worship the Lich King as a god.
To help the Archmage accomplish his mission, Ner'zhul left Kel'Thuzad's humanity intact.
The aged, yet still charismatic wizard, was charged with using his powers of illusion and persuasion to lull the downtrodden, disenfranchised masses of Lordaeron into a confidence.
Once he had their attention, he would offer them a new vision of what society could be - and a new figurehead to call their king.
Kel'Thuzad returned to Lordaeron in disguise, and over the span of three years, he used his fortune and intellect to gather a clandestine brotherhood of like-minded men and women.
The brotherhood, which he called the Cult of the Damned, promised its acolytes social equality and eternal life on Azeroth in exchange for their service and obedience to Ner'zhul.
 
As the months passed, Kel'Thuzad found many eager volunteers for his new cult amongst the tired, overburdened laborers of Lordaeron.
Surprisingly, Kel'Thuzad's goal to pervert the citizens' faith in the Holy Light towards belief in Ner'zhul's dark shadow was easily attained.
As the Cult of the Damned grew in size and influence, Kel'Thuzad made sure to keep its workings secret from the authorities of Lordaeron at every turn.
With Kel'Thuzad's success in Lordaeron, the Lich King made the final preparations for his assault against the human civilization.
Placing his plague energies into a number of portable artifacts called Plague Cauldrons, Ner'zhul ordered Kel'Thuzad to transport the cauldrons to Lordaeron where they would be hidden within various cult-controlled villages.
The cauldrons, protected by the loyal cultists, would then act as plague generators by sending the plague seeping out across the unsuspecting farmlands and cities of northern Lordaeron.
The Lich King's plan worked perfectly.
Many of Lordaeron's northern villages were contaminated almost immediately.
Just as in Northrend, the citizens who contracted the plague died and arose as the Lich King's willing slaves.
The cultists under Kel'Thuzad were eager to die and be raised again in their dark lord's service.
They exulted in the prospect of immortality through undeath.
As the plague spread, more and more feral zombies arose in the northlands.
Kel'Thuzad looked upon the Lich King's growing army and named it the Scourge - for soon, it would march upon the gates of Lordaeron and scour humanity from the face of the world.
Kel'Thuzad, upon the Lich King's instruction, oversaw the infection of the small town of Brill where he was discovered by Jaina Proudmoore and Prince Arthas.
From there he quickly fled and they followed him back to Andorhal, where he told Arthas of Mal'ganis in Stratholme.
Arthas, in a rage, hunted Kel'Thuzad down and killed him, but not before Kel'thuzad told him his death would mean little.

Arthas ultimately betrayed his kingdom and become a servant of the Lich King.
Kel'Thuzad began to appear to him as a ghostly apparition after his protector, Gavinrad the Dire, was slain by Arthas and Kel'thuzad's remains were reclaimed.
He appeared only to Arthas, and told him that he was not to trust the dreadlords, promising to explain all of the Lich King's plans to Arthas once he walked the earth again in Quel'Thalas.
Kel'Thuzad watched over Arthas as he made the slow procession to the Sunwell in Silvermoon against the stratagems of Sylvanas Windrunner.
Eventually, Arthas ravaged his way through the two Elfgates and finally laid siege to Silvermoon itself, breaching through to the fabled Sunwell.
Arthas placed Kel'thuzad's remains within the well, and with the help of Tichondrius, Kel'Thuzad was reborn into the terrifying form of a lich.

As they traveled to Alterac, Kel'Thuzad explained that the Scourge was merely the harbinger of the Burning Legion, and that he would summon the first of the demons, the eredar warlock Archimonde to the mortal world.
After slaying the orcs guarding the Demon Gate, Kel'Thuzad communed with the dark lord who told him that he must go to Dalaran and steal the Book of Medivh.
After Arthas led the attack on Dalaran and killed Antonidas, the book was retrieved and Kel'Thuzad began the lengthy summoning process, with Arthas defending him from the many attacks of Dalaran and the Kirin Tor. When all was complete, Archimonde stepped through the portal and was free to act according to his plans.
His first act was to promote Tichondrius to leader of the Scourge, rendering Arthas and Kel'Thuzad of little use.
However, Kel'Thuzad, confident in the Lich King's grand design, disappeared amidst the chaos of Dalaran's destruction.
Kel'Thuzad resurfaced as the Legion raked across the Plaguelands, and in the aftermath of the invasion, he remained in the Capital as one of the Lich King's lieutenants.
Arthas had gone to Kalimdor on Ner'zhul's command, and so only Kel'Thuzad and the banshee Sylvanas Windrunner remained in his stead.
But they knew that the Legion was defeated long before the Dreadlords who remained in Lordaeron did.
Arthas returned in a fury and chased the dreadlords out of the Capital, and Kel'Thuzad was relieved to see him.
With the Legion's generals gone, they turned to the human villages who were escaping to the mountain passes.
Kel'Thuzad thought that perhaps they would be a fitting sacrifice to the Lich King.
But as they cut a swath through the human forces, Arthas suffered some violent seizures, and Kel'Thuzad considered recalling their forces, but the King forbade it, and they continued on their macabre mission. In the aftermath, Arthas received a vision from Ner'zhul, who told him to return to Northrend.
Kel'Thuzad immediately prepared for his departure, but they were abruptly ambushed by the dreadlords, and separated.
The dreadlords unleashed their forces against Arthas, but Kel'Thuzad found his own way out of the city.

Kel'Thuzad later came upon Arthas in the clutches of Sylvanas and her wicked banshees.
She was about to strike when Kel'Thuzad unleashed his forces against her and her sisters.
With the banshees dead, Sylvanas was forced to retreat.
Kel'Thuzad escorted Arthas to the shore, where he had prepared a fleet of ships for his departure.
Arthas asked Kel'Thuzad, as his most loyal servant and twisted friend, to remain in Lordaeron and ensure that his legacy remain.
Kel'Thuzad swore on what was left of his life to carry out that mission at any cost. In the battle that would follow between Sylvanas and the dreadlords, Kel'Thuzad took his forces into hiding, where he would plot his resurfacing into the new powers of the Plaguelands.
He resided in his necropolis Naxxramas, above Stratholme.
After the events of the original WoW, he and his necropolis moved to Northrend,where they await foolish travelers who are seeking glory in the cold region of Dragonblight. 

Trivia

As all of the charachters in Warcraft 3,Kel'Thuzad had is own set of gag quotes: